AIDS and other serious infectious diseases have created an urgent need for a medical syringe which may be safely disposed or discarded following usage. There is an associated requirement, after such usage, for a simple means to permit a manual withdrawing of the needle up inside of the syringe barrel and locking same so as to provide two functions; the first is safety related, i.e. the point of the needle is withdrawn up within the syringe barrel so as to prevent an accidental sticking of medical staff or other personnel. The second function is to have the first safety means "unlockable" so as to prevent a used syringe from being used again, e.g. from surreptitiously being obtained by a drug addict for use thereby and possible sharing with other addicts.
There has been a general need for such a safety syringe for some time, as is evidenced by a number of prior art patents to be identified below. However, there has been a relatively recent increased awareness and understanding of AIDS, with the associated recognition that one of the principal ways of acquiring the AIDS related virus in one's body is via the "use" of a needle of an AIDS contaminated syringe. Such "use" may be intentional, such as drug addicts sharing needles. On the other hand, the "use" can be completely unintentional or accidental, e.g. medical staff personnel in a hospital emergency room being accidentally stuck by the needle of a syringe following use of the syringe on an accident victim who, after the fact, is determined to have the AIDS virus. An indication of the severity of the problem, with a special focus on the aforesaid drug addicts, is a January 1988 report by the New York Times which states, in part, that one out of every 61 babies born in New York City during December 1987 carried antibodies to the AIDS virus, indicating that their mothers were infected. The report further states that most infected women contract the human immunodeficiency virus or HIV, which is believed to cause AIDS, by sharing contaminated needles in drug abuse or by sexual intercourse with an infected male drug user.
In short, the above described problem is extremely serious. As is well known, the consequences of one accidentally acquiring AIDS are always profound and sometimes terminal.
A sampling of prior art, syringe patents which attempt to respond to the above identified need, but fall short in various ways, are U.S. Pat. Nos. 2,888,923 Reis; Lesson, et al, 3,890,971; Haller 4,026,287; Staempfli 4,391,272; Vining et al 4,507,117; Jennings, Jr. 4,650,468; and DeLuccia 4,675,005.
Using DeLuccia U.S. Pat. No. 4,675,005 as an example of a prior art syringe which falls short of the mark, a needle assemble is screwed into one threaded end of a syringe barrel assembly; in one embodiment a plunger means is arranged so as to transmit torque from the plunger to the needle assembly so as to screw the needle assembly out of threaded engagement with the barrel and then the plunger and attached needle assembly is moved axially all the way to the opposite end of the barrel at which point the plunger is rotated some additional revolutions so as to attach, through additional threaded means, the plunger to the barrel. The needle assembly follows with the plunger assembly and (as is shown in FIG. 4 of DeLuccia) the needle is totally brought inside the syringe barrel so as to provide safety. However, a threshhold problem of the DeLuccia syringe is that the plunger and needle assembly, after being withdrawn up into the barrel, as is shown in FIG. 4 thereof, is not truly locked. To the contrary, human desired to reuse the needle it is simply necessary to reverse the order of usage, namely, decoupling the plunger assembly from the end of the barrel following which the plunger and needle assembly may be moved axially so that the needle once again is projecting out through opening 42. The DeLuccia apparatus also is expensive to manufacture and complicated and time consuming to use, two important factors which rule against acceptance by professionals in the medical services field.